The invention relates to a particularly simple device for checking the temperature within an enclosure, whenever the temperature has to be maintained in an allowed range between two extreme values. Such may be the case for monitoring the temperature in a refrigeration enclosure, more particularly a refrigerator. As strange as it may seem, most refrigerators are delivered to their customers without a simple device for checking the temperature within these enclosures. Most of these refrigeration enclosures are generally provided with means, especially control knobs, allowing adjustment of the temperature to values which can a priori be stepped over a certain range of values. But the choice of these values for most users is often completely empirical.
However, it is known that in order to preserve food satisfactorily, the temperature has to be maintained, for example within a domestic refrigerator, at a value lying between approximately 2.degree. C. and 60.degree. C.